The application of the geographic and hydrological method has shown that evaporation, like evaporation, varies greatly even in one natural zone, since the assimilation of solar radiation by the earth's surface depends on many factors.
In Northern Europe, evaporation is close to its upper limit - evaporation - about 100 mm per year. In the zone of dry steppes of the South-East of Europe, as well as in the arid regions of the Mediterranean subtropics, the evaporation reaches 1200-1300 mm, and the actual evaporation due to lack of moisture is only 300 mm. Moisture deficit - the difference between precipitation and evaporation in arid zones is 600-800 mm.
In the Baltics, evaporation is 300-350 mm, and in the Central regions of the Russian Plain 400 mm.
The maximum evaporation, of course, is in deserts, especially in the Sahara. In its central parts it exceeds 4500 mm. Evaporation, limited by an insignificant amount of precipitation, does not exceed 100 mm per year. Here, not only precipitation is consumed for evaporation, but also groundwater flowing from the Atlas Mountains and from the Central African basin. The difference between potential (4500) and actual (about 100 mm) evaporation expresses the degree of dryness of the Sahara.
The greatest evaporation(about 1200 mm) occurs in the swampy lowlands of Central Africa - in the basin of Lake Chad and the Upper Nile. Plants provided here with warmth and moisture. They give the largest increase in plant mass on Earth. In equatorial Africa, a layer of water of 1000 mm evaporates per year.
In the Amazon basin, evaporation is from 1200 to 1500 mm, and in the south of Argentina it drops to 200 mm. In Central America from 1000 to 1500 mm, in the humid east of the USA from 600 to 1000, in the prairies 200-300, and in California 200 mm. In Hindustan and Indochina 800-1000 mm, in East Asia 400-600. in Central - 100-200. and in the subpolar 50-100 mm. The lowest evaporation in Australia: 100-200 mm in Central and 800-1000 mm in Eastern. During the year, a layer of 1020 m 3 evaporates from the Earth's surface as a whole, which in volume terms corresponds to 518,600 km 3. On the ocean, its thickness reaches 1260 mm, or 447,900 km 3, and on the mainland it decreases to 420 mm (71,770 km 3), including 558 mm, or 71,040 km 3 in peripheral drainage areas, and 240 mm in areas of internal drainage. , or 740-730 km 3 .
In terms of the intensity of evaporation, the oceanic surface differs sharply from the continental surface. To this it should be added that evaporation on the oceans coincides with evaporation. Later we will see that the main mass of precipitation on the continents is moisture brought directly from the ocean, and not delivered by intracontinental moisture cycles.
The generalized zonal characteristic of evaporation is as follows: the largest layer (up to 2000 mm) evaporates in tropical oceans, which is caused by intense solar radiation in a cloudless sky and the continuous removal of moisture by the trade winds. On land in these latitudes solar radiation causes such a large evaporation that cannot be satisfied by the processes of continental moisture circulation. As a result, a desert climate is formed with a sharp difference between the need and the availability of water.
In the equatorial zone, due to cloudiness and calmness, evaporation decreases to 1000 mm both on the ocean and on land. In the subequatorial zone, under local favorable conditions for the inflow of carved and underground water (Chad. Upper Nile), evaporation reaches a maximum value for land.
In the temperate zone of the northern hemisphere in the desert zone, evaporation is about 200 mm or less, in the forest zone - from 300 to 500 mm, and in the tundra again decreases to 100 mm. In deserts, low evaporation is caused by a lack of moisture, in the tundra - a lack of heat.
Evaporation It consists in the transition of water from a liquid or solid phase to a gaseous one and in the entry of water vapor into the atmosphere.
Evaporation is an energy process. It depends on the amount of thermal energy that can be spent on a given surface per unit time, and is determined, therefore, by the equation heat balance on earth's surface. On the oceans, up to 90% of the energy of solar radiation is spent on evaporation.
The second meteorological condition that determines the amount of evaporation is the moisture content of the air, the degree of its dryness or humidity. Quantitatively, it is characterized by a moisture deficit, which in turn depends on the air temperature and, to a lesser extent, on the wind. Of course, evaporation can only occur in the presence of water. On land, this condition is far from being present everywhere and not always: arid zones are characterized by a moisture deficit, and in humid zones, moisture may be lacking in certain periods. In this regard, in meteorology, the concept of volatility (Ec).
Evaporation - this is the maximum possible evaporation under given meteorological conditions, not limited by moisture reserves. The same applies to the term "potential evaporation".
Evaporation is one of the most important processes geographical envelope. It consumes most of the sun's heat. . The latent heat of vaporization, released during moisture condensation, heats the atmosphere, and this heat source for the atmosphere is the main one. Evaporated moisture enters the continents and provides them with precipitation. During phase transitions of water, heat is absorbed or released, and during atmospheric circulation it is redistributed. One of the types of evaporation - transpiration - is involved in biological processes and the formation of biological mass.
The climatic and, especially, biophysical significance of evaporation lies in the fact that it shows the drying ability of air: the more it can evaporate with limited moisture reserves in the soil, the more pronounced aridity. In some places, this leads to the appearance of deserts, in others it causes temporary droughts, and thirdly, where evaporation is negligible, waterlogged conditions are created.
In Northern Europe, evaporation is close to its upper limit - evaporation - about 100 mm per year. In the zone of dry steppes of the South-East of Europe, as well as in the arid regions of the Mediterranean subtropics, evaporation reaches 1200 - 1300 mm, and the actual evaporation due to lack of moisture is only 300 mm. Moisture deficiency - the difference between precipitation and evaporation in arid zones is approximately 600-800 mm.
The maximum evaporation, of course, is in deserts, especially in the Sahara. In its central parts it exceeds 4500 mm. Evaporation, limited by an insignificant amount of precipitation, does not exceed 100 mm per year. Here, not only precipitation is consumed for evaporation, but also groundwater flowing from the Atlas Mountains and from the Central African basin. The difference between potential (4500 mm) and actual (about 100 mm) evaporation expresses the degree of dryness of the Sahara.
The greatest evaporation (about 1,200 mm) occurs in swampy lowlands Central African-in basin of Lake Chad and the Upper Nile. Plants provided here with heat and moisture give the largest increase in plant mass on Earth. In equatorial Africa, a layer of water of 1000 mm evaporates per year.
Evaporation and evaporation reflect both the precipitation regime and the heat regime. The ratio of the input and output of atmospheric moisture is called atmospheric humidification.
Evaporation and evaporation. Geographic distribution of evaporation and evaporation (analysis of maps of evaporation and evaporation)
EVAPORATION (Russian) - the transition of a substance from a liquid or solid state to a gaseous state - to steam. In nature, water vapor enters the atmosphere from the surface of water, soil, vegetation, ice, and snow. Evaporation depends on the temperature and humidity of the air, on the evaporating surface and wind speed.
EVAPORATION - the maximum possible evaporation under given meteorological conditions from a sufficiently moist underlying surface, that is, under conditions of an unlimited supply of moisture. Evaporation is expressed in millimeters of evaporated water and is very different from actual evaporation, especially in the desert, where evaporation is close to zero and evaporation is 2000 mm per year or more.
Heat is expended on evaporation, as a result of which the temperature of the evaporating surface decreases. This is of great importance for plants, especially in equatorial-tropical latitudes, where evaporation reduces their overheating. The southern oceanic hemisphere is colder than the northern partly for the same reason.
The daily and annual course of evaporation is closely related to air temperature. Evaporation values in polar latitudes of about 60-80 mm with a maximum value of 100-120 mm are due to low air temperatures and, as a result, close values of E1 (actual water vapor elasticity) and e (maximum elasticity).
In the polar regions, at low temperatures of the evaporating surface, both the saturation elasticity Es and the actual elasticity e are small and close to each other. Therefore, the difference (Es - e) is small, and together with it, the volatility is small. In Svalbard it is only 80 mm per year, in England about 400 mm, in Central Europe about 450 mm. On the European territory of Russia, evaporation increases from northwest to southeast along with an increase in moisture deficit. In Leningrad it is 320 mm per year, in Moscow 420 mm, in Lugansk 740 mm. IN Central Asia with its high summer temperatures and large moisture deficit, evaporation is much higher: 1340 mm in Tashkent and 1800 mm in Nukus.
In the tropics, evaporation is relatively low on the coasts and increases sharply in the interior of the continents, especially in deserts. So, on the Atlantic coast of the Sahara, the annual evaporation is 600-700 mm, and at a distance of 500 km from the coast - 3000 mm. In the most arid regions of Arabia and the deserts of Colorado, it is higher than 3000 mm. Only in South America there are no areas with an annual evaporation rate of more than 2500 mm.
At the equator, where the moisture deficit is small, evaporation is relatively low: 700-1000 mm. In the coastal deserts of Peru, Chile, and South Africa, annual evaporation is also no more than 600-800 mm.
The geographical distribution of actual evaporation in latitudes is as follows:
At a latitude of 0-10 °, evaporation on land is 112 cm, in the ocean - 110 cm.
At a latitude of 20-30 °, evaporation on land is 37 cm, in the ocean - 130 cm.
At a latitude of 40-50 °, evaporation on land is 37 cm, in the ocean - 70 cm.
At a latitude of 60-90 °, evaporation on land is 8 cm, in the ocean - 15 cm.
Chapter 8
Water in the atmosphere
Evaporation and evaporation
Water, which is part of the air, is in it in a gaseous, liquid and solid state. It enters the air due to evaporation from the surface of water bodies and land (physical evaporation), as well as due to transpiration (evaporation by plants), which is a physical and biological process. Surface layers of air enriched
Rice. 37. Average annual values of evaporation from the underlying surface (mm/year)
water vapor, become lighter and rise up. As a result of the adiabatic decrease in the temperature of the rising air, the content of water vapor in it, in the end, becomes the maximum possible. Condensation, or sublimation, of water vapor occurs, clouds form, and from them - precipitation that falls to the ground. This is how the water cycle works. Water vapor in the atmosphere is renewed on average about every eight days. An important link in the water cycle is evaporation, which consists in the transition of water from a liquid or solid state of aggregation (sublimation) to a gaseous state and the entry of invisible water vapor into the air.
Evaporation shows the actual amount of evaporating water as opposed to is-
1 Humid air is slightly lighter than dry air because it is less dense. For example, air saturated with water vapor at a temperature of 0 ° and a pressure of 1000 mb is less dense than dry air - by 3 g / m (0.25%). At higher temperatures and correspondingly higher moisture content, this difference increases.
soaring- the maximum possible evaporation, not limited by moisture reserves. Therefore, evaporation over the oceans is almost equal to evaporation. intensity or evaporation rate called the amount of water in grams, evaporating from 1 cm of the surface per second (V \u003d r / cm2 in s). Measuring and calculating evaporation is a difficult task. Therefore, in practice, evaporation is taken into account in an indirect way - according to the size of the water layer (in mm), evaporated over longer periods of time (day, month). A layer of water of 1 mm from an area of 1 m is equal to a mass of water of 1 kg. Evaporation rate s water surface depends on a number of factors: 1) on the temperature of the evaporating surface: the higher it is, the greater the speed of movement of molecules and a greater number of them break away from the surface and enter the air; 2) from the wind: the greater its speed, the more intense the evaporation, since the wind carries moisture-saturated air and brings drier air; 3) from the lack of humidity: the more it is, the more intense the evaporation; 4) on pressure: the larger it is, the less evaporation, since it is more difficult for water molecules to break away from the evaporating surface.
When considering evaporation from the soil surface, it is necessary to take into account such physical properties as color (dark soils evaporate more water due to high heating), mechanical composition (loamy soils have higher water-lifting capacity and evaporation rate than sandy soils), humidity (than the soil is drier, the less evaporation). Also important are such indicators as the level of groundwater (the higher it is, the greater the evaporation), the relief (in elevated places the air is more mobile than in the lowlands), the nature of the surface (rough compared to smooth has a larger evaporating area), vegetation, which reduces evaporation from the soil. However, plants themselves evaporate a lot of water, taking it from the soil with the help of the root system. Therefore, in general, the influence of vegetation is diverse and complex.
Heat is expended on evaporation, as a result of which the temperature of the evaporating surface decreases. This is of great importance for plants, especially in equatorial-tropical latitudes, where evaporation reduces their overheating. The southern oceanic hemisphere is colder than the northern partly for the same reason.
The daily and annual course of evaporation is closely related to air temperature. Therefore, the maximum evaporation during the day is observed
It is around noon and is well expressed only in the warm season. In the annual course of evaporation, the maximum falls on the warmest month, the minimum - on the coldest. In the geographical distribution of evaporation and evaporation, which depend primarily on temperature and water reserves, there is zonation(Fig. 37).
In the equatorial zone, evaporation and evaporation over the ocean and land are almost the same and amount to about 1000 mm per year.
In tropical latitudes, their average annual values are maximum. But highest values evaporation - up to 3000 mm are noted over warm currents, and evaporation of 3000 mm - in the tropical deserts of the Sahara, Arabia, Australia, with actual evaporation of about 100 mm.
In temperate latitudes over the continents of Eurasia and North America evaporation is less and gradually decreases from south to north due to lower temperatures and deeper into the continents due to a decrease in moisture reserves in the soil (in deserts up to 100 mm). Evaporation in deserts, on the contrary, is maximum - up to 1500 mm / year.
In polar latitudes, evaporation and evaporation are small - 100 - 200 mm and are the same over sea ice Arctic and over land glaciers.
moisture circulation
The initial source of atmospheric moisture is the World Ocean, from the surface of which water evaporates. Part of it condenses in clouds and falls out as precipitation right there on the ocean, completing a small moisture cycle. Another part of the evaporated moisture in the form of water vapor is transferred to land, where it also condenses in clouds and falls in the form of liquid or solid precipitation, seeps into the ground, flows into rivers into the ocean and is consumed by plants and animals. This link in the moisture cycle is not closed, since most of the water vapor in the process of photosynthesis is decomposed by plants into hydrogen and oxygen, and the smaller part is bound, irrevocably excluding it from water exchange. Quantitatively, moisture circulation is characterized water balance.
Water balance - ϶ᴛᴏ the algebraic sum of all forms of moisture inflow and outflow in the atmosphere, on a selected territory or on the sea, on a continent or ocean, and on the earth's surface as a whole.
Precipitation (P) that falls on the territory partially evaporates (E) into the atmosphere, partially drains (R): into the ocean
P=E+R
that is, precipitation is equal to evaporation plus runoff. This is the water balance. The above equation was proposed by A. I. Voeikov in 1884 ᴦ.
In 1932 ᴦ. G. N. Vysotsky proposed an equation in which evaporation and runoff are divided into their component parts. Evapotranspiration E consists of direct evaporation E n and transpiration T:
E \u003d Yong + T.
Full stock R was divided into superficial S and underground u :
K = S + U.
The reserve or lack of groundwater in previous years also takes part in the water balance of the territory. ±W.
Today, the water balance formula looks like:
P = En + T + S + U ±W
The complete equation of the water balance of a limited area includes (in addition to the components already listed) condensation of moisture on the surface, surface inflow, underground inflow, changes in water reserves in the snow cover, the same in swamps, water intake, transfer to other systems and return of water from economic needs. With the help of a few components, it reflects the diverse relationship between water, atmospheric air, soil and vegetation.
Evaporation It consists in the transition of water from a liquid or solid phase to a gaseous one and in the entry of water vapor into the atmosphere.
Evaporation is primarily an energy process. It depends on the amount of thermal energy that can be spent on a given surface per unit time, and is determined, therefore, by the heat balance equation on the earth's surface. On the oceans, up to 90% of the energy of solar radiation is spent on evaporation.
The second meteorological condition that determines the amount of evaporation is the moisture content of the air, the degree of its dryness or humidity. Quantitatively, it is characterized by a moisture deficit, which in turn depends on the air temperature and, to a lesser extent, on the wind. Of course, evaporation can only occur in the presence of water. On land, this condition is far from being present everywhere and not always: arid zones are characterized by a moisture deficit, in humid zones moisture may be lacking in certain periods. In this regard, in meteorology, the concept of volatility (Ec).
Evaporation - ϶ᴛᴏ the maximum possible evaporation under given meteorological conditions, not limited by moisture reserves. The same applies to the term "potential evaporation".
Evaporation is one of the most important processes of the geographic envelope. It consumes most of the sun's heat. . The latent heat of vaporization, released during moisture condensation, heats the atmosphere, and this source of heat for the atmosphere is the main one. Evaporated moisture enters the continents and provides them with precipitation. During phase transitions of water, heat is absorbed or released, and during atmospheric circulation it is redistributed. One of the types of evaporation - transpiration - takes part in biological processes and the formation of biological mass.
The climatic and, especially, biophysical significance of evapotranspiration lies in the fact that it shows the drying ability of air: the more it can evaporate with limited moisture reserves in the soil, the more pronounced aridity is. In some places, this leads to the appearance of deserts, in others it causes temporary droughts, and thirdly, where evaporation is negligible, waterlogged conditions are created.
In Northern Europe, evaporation is close to its upper limit - evaporation - about 100 mm per year. In the zone of dry steppes of the South-East of Europe, as well as in the arid regions of the Mediterranean subtropics, evaporation reaches 1200 - 1300 mm, and the actual evaporation due to lack of moisture is only 300 mm. Moisture deficiency - the difference between precipitation and evaporation in arid zones is approximately 600-800 mm.
The maximum evaporation, of course, is in deserts, especially in the Sahara. In its central parts it exceeds 4500 mm. Evaporation, limited by an insignificant amount of precipitation, does not exceed 100 mm per year. Here, not only precipitation is consumed for evaporation, but also groundwater flowing from the Atlas Mountains and from the Central African basin. The difference between potential (4500 mm) and actual (about 100 mm) evaporation expresses the degree of dryness of the Sahara.
The greatest evaporation (about 1,200 mm) occurs in the swampy lowlands of Central Africa, in the basin of Lake Chad and the Upper Nile. Plants provided here with heat and moisture give the largest increase in plant mass on Earth. In equatorial Africa, a layer of water of 1000 mm evaporates per year.
Evaporation and evaporation reflect both the precipitation regime and the heat regime. The ratio of the inflow and outflow of atmospheric moisture is commonly called atmospheric humidification.